Synergetic Crest Factor Reduction and Baseband Digital Predistortion for Adaptive 3G Doherty Power Amplifier Linearizer Design

A novel approach for power amplifier (PA) characterization suitable for single iteration digital predistorter synthesis is proposed. This approach consists of synergetic crest factor reduction and baseband digital predistortion to avoid the average power variation at the input of the PA between the characterization and linearization steps. This is achieved by bypassing the crest factor reduction block during the characterization step and by applying it concurrently with digital predistortion in the linearization step. First, the PA´s behavior sensitivity to the average input power is evaluated. The limitations of conventional approaches for the PA characterization, in the context of single iteration digital predistortion, are then demonstrated. The performance of the proposed technique is validated experimentally on a 300-W peak PA. The measured improvement of the adjacent channel power ratio at the output of the linearized amplifier is 16 dBc for the conventional approach and 29 dBc for the proposed approach.